LAS VEGAS  Bill Gates traditionally uses his annual Comdex speech to make big announcements about new Microsoft products, but this year much of his keynote address was dedicated to solving old problems.

Speaking to thousands last night at the Aladdin Casino, Gates addressed two issues plaguing Microsoft for years: security weaknesses and spam. Both became more irritating  and costly  this year for Microsoft and its customers as the volume of spam exploded and worms like Blaster devastated computer systems.

"These are software problems," he said. "They're not easy software problems to solve."

Gates' 75-minute speech kicked off this week's Comdex, an annual technology-industry convention that runs through Thursday. About 50,000 attendees are expected for the event, which has been significantly scaled down and refocused on business networking and deal making.

Gates announced new spam-filtering technology called SmartScreen. Developed by Microsoft's research division, it will be included in all of the company's e-mail products. The technology uses new ways to scan and detect junk e-mail before it hits a customer's inbox.

It is a milestone of sorts for the group Microsoft formed early this year to develop spam-fighting technologies using scientific computations.

For months, the group has also collected comments from Hotmail and MSN subscribers about whether certain messages coming into their inboxes are spam.

The anti-spam technology will be available in an upcoming version of Microsoft's Exchange Server, Gates said.

"We believe these new approaches will shift the tide" in the war on spam, he said. These technological advancements and the prosecution of spammers will make the business of spamming less attractive, he said.

Gates also unveiled a firewall system, the Internet Security and Acceleration Server 2004, whose purpose is to protect against Internet attacks. He said the server goes farther than a classic firewall in what it can do. It is an upgrade from a version released in 2000 and features new levels of application security and simpler management.

A test version of the software is expected in January. The company has not given a date for a final version release.

'Seamless computing'

Microsoft has turned plenty of computing-related terms into catchphrases, and Gates introduced a new one yesterday: "seamless computing."

The phrase is yet another variation on an idea Microsoft has talked about for years: Software and devices should match the way people work and live. The theme seems nearly identical to the company's oft-stated goal of empowering people through software any time, any place and on any device.

Seamless computing is already evident in the Media Center PC, a personal computer focused on playing music and watching movies and television, Gates said.

The idea also is key to Microsoft's Smartphones, he said, which combine a personal digital assistant with a cellphone; and the upcoming Smart Personal Objects Technology (SPOT), which constantly updates news, calendars and traffic reports to watches and other devices.

By removing problematic "seams," Gates said, "we can deliver all the scenarios that we dreamed about since this industry got started."

A highlight of Gates' speech last year was the introduction of the Tablet PC portable computer. He announced yesterday a free software upgrade to the Tablet informally called version 1.5.

The upgrade, expected in mid-2004, will give users more flexibility when writing on the screen with the "digital ink" tool. It will have some minor redesigns and allow software developers to add inking capabilities to existing applications.

Microsoft hasn't disclosed Tablet PC sales in the past year, but there are indications the machine isn't selling well in some parts of world.

According to a report earlier this month by British research company Canalys, about 92,000 Tablet PCs had shipped in Europe, the Middle East and Africa by the end of September. Third-quarter shipments fell 20 percent from those in the second quarter, the report said.

The report did not discuss Tablet PC sales in the United States.

Tablet PC makers are expected to include the new software in their machines, although some appear to be a bit grumpy about the system these days. The president of Taiwan computer maker Acer reportedly said Microsoft is charging too much for the operating system, which has slowed sales.

Other makers have hinted at lower-than-expected sales in the past.

Gates said the Tablet PC is on its way to becoming a must-have for some workers, and that there is "a lot of evolution taking place" with the device.

'Stuff I've Seen' and other stuff

Gates also spent some of last night's speech on futuristic inventions, particularly a technology he called "Stuff I've Seen."

Started as a project in Microsoft's research division, it catalogs information about what users see on a computer  Web sites and e-mail, for example  so that they can go back and search the data.

The program could also open a window on a computer screen with a list of items useful for certain tasks. If a person was writing an e-mail to a co-worker, for example, a window could display a list of past e-mails to the co-worker or the co-worker's last office presentation.

Gates didn't say when the technology might be sold but hinted it could become part of the next version of Windows. That version, code-named Longhorn, isn't expected to be released until 2005 or 2006, although Gates said yesterday he would not give a time frame for a release date.

A tradition in Gates' Comdex speech is a humorous video. They've satirized pop culture and included cameos from celebrities.

This year, the video spoofed the "Matrix" movies, featuring Microsoft Chief Executive Steve Ballmer as the protagonist Neo, and Gates as the mentor Morpheus.

In the video, Gates asked Ballmer to choose between swallowing a palm-size blue pill with IBM's logo on it, and a tiny red pill with a Microsoft logo on it.

And, perhaps with unintended irony, Gates said to Ballmer: "You will need to learn a new way of thinking, one that allows you to recognize the rules of the Matrix but bend those rules to your will."

Some of Microsoft's competitors might argue the company has already learned that lesson.